Factor Analysis Demonstrates a Common Schizoidal Phenotype within Autistic and Schizotypal Tendency: Implications for Neuroscientific Studies

Abstract

Behavioral and cognitive dysfunction, particularly social and communication impairments, are shared between autism and schizophrenia spectrum disorders, while evidence for a diametric autism-positive schizophrenia symptom profile is inconsistent. We investigated the shared phenotype at a personality trait level, particularly its resemblance to schizoid personality disorder, as well as differential aspects of the autism–schizophrenia model. Items of the autism spectrum quotient (AQ) and schizotypal personality questionnaire (SPQ) were pseudo-randomly combined, and were completed by 449 (162 male, 287 female) non-clinical participants aged 18–40. A factor analysis revealed three factors; the first represented a shared social disorganization phenotype, the second reflected perceptual oddities specific to schizotypy while the third reflected social rigidity specific to autism. The AQ and SPQ were strongly correlated with Factor 1 (AQ: r = 0.75, p < 0.001; SPQ: r = 0.96, p < 0.001), SPQ score was correlated with Factor 2 (r = 0.51, p < 0.001), particularly in cognitive–perceptual features (r = 0.66, p < 0.001), and AQ score was strongly correlated with Factor 3 (r = 0.76, p < 0.001). Furthermore, there was no relationship between Factor 1 and Factor 2. Thus, there is robust evidence for a shared social disorganization phenotype in autistic and schizotypal tendency, which reflects the schizoid phenotype. Discriminating and independent dimensions of schizotypal and autistic tendency exist in Factors 2 and 3, respectively. Current diagnostic protocols could result in different diagnoses depending on the instrument used, suggesting the need for neuromarkers that objectively differentiate autistic and schizotypal traits and resolve the question of commonality versus co-morbidity.

The diagnostic boundary between autism spectrum disorder, intellectual developmental disorder and schizophrenia spectrum disorders

“…There seems to be a relationship between the mean level of autistic symptoms and schizotypal traits, as well as specific associations between autistic symptoms and negative, disorganized and positive schizotypal symptoms (Ford and Crewther, 2014). Patients diagnosed with an ASD show schizophrenia spectrum traits in adolescence.…”

Psychosocial deficits across autism and schizotypal spectra are interactively modulated by excitatory and inhibitory neurotransmission

“…Participant recruitment and experimental procedures have been reported previously (Ford & Crewther, 2014;Ford et al, 2017b). Briefly, 38 non-clinical participants (18 males, 20 females; mean age [SD] = 23.22 [5.52]) were recruited for the 1 H-MRS component of a much larger study of 1,678 young adults aged 18-40 years (Ford et al, 2017b) based on their scores on a questionnaire of pseudo-randomized Autism-Spectrum Quotient (AQ) and Schizotypal Personality Questionnaire (SPQ) items (Ford & Crewther, 2014). Participants were recruited for the larger study via social media and on-campus advertising and were invited to complete the online questionnaire.…”

“…The AQ is a 50-item scale that quantifies autistic tendency across five subscales: social skill, communication, attention switching, attention to detail, and imagination (Baron-Cohen, Wheelwright, Skinner, Martin, & Clubley, 2001). Responses to AQ items were given on a 4point Likert scale from 1 (strongly disagree) to 4 (strongly agree), with original scores preserved -rather than scaling as per the original scoring system -to generate a total score out of 200 and to improve response reliability (Cronbach's alpha = .82) (Austin, 2005;Ford & Crewther, 2014).…”

Mismatch field latency, but not power, may mark a shared autistic and schizotypal trait phenotype

“…Autism and schizophrenia are spectrum disorders with symptom phenotypes readily identified as traits in the non-clinical population. There is increasing evidence for substantial phenotypic overlap between the two disorders, particularly in the negative symptom domain of schizophrenia, and social and communication deficit domain of autism (Dinsdale et al, 2013;Kanai et al, 2011;Spek and Wouters, 2010;Wakabayashi et al, 2012;Ford and Crewther, 2014). At a trait level, a shared autistic and schizotypal phenotype has been identified through factor analysis of the autism spectrum quotient (AQ: (Baron-Cohen et al, 2001)) and schizotypal personality questionnaire (SPQ: (Raine, 1991)).…”